The current proposal is a logical extension of previous research using the RIP-LCMV model for virus-induced autoimmune diabetes to analyze pathogenic mechanisms and define novel immuno-therapeutic approaches for IDDM. The most promising areas were identified and form the specific aims of this application: The first goal is to precisely define which effect cytokines produced in the islets have at different times during the development of diabetes. Recent reports have described controversial effects for TNF-(alpha), IL-10, TGF-(beta) and others. In the majority of these transgenic models it has been impossible to control, when and at what level the cytokine is produced. The applicant proposes to use novel transgenic mice that express cytokines under a tetracycline sensitive regulatory promoter and cross these with the RIP-LCMV model. Further, the role of stat-4 (IL-12) and stat-6 (IL-4) pathways that represent two key cytokines implicated in the pathogenesis of IDDM will be analyzed by mating stat-4 or -6 deficient mice to RIP-LCMV transgenics. The second aim is to test and improve immunotherapies for autoimmune diabetes. Promising preliminary results were obtained by treating RIP-LCMV mice with antibodies to B7.1, B7.2 or CD40L systemically, which abrogated development of IDDM without affecting primary systemic activation of autoreactive (LCMV-specific) lymphocytes. Further, treatment with anti-CD3Fa/b(2) will be attempted, because regulatory cells can be induced preferentially by anti-CD3. Lastly, it will be attempted to increase the efficacy of "oral tolerance" by administration of insulin coupled to cholera toxin B subunit. Preliminary studies look encouraging indicating more than 10-fold lower antigenic requirements. Since the oral effect of the insulin maps to the B-chain and the likely mechanism is induction of regulatory Lymphocytes that act as "bystander suppressors". Preliminary studies also indicate that the systemic application of plasmids expressing the insulin B-chain should have a therapeutic effect, which is reflected by the preliminary data. It is felt that RlP-LCMV model is an ideal tool for addressing these issues, because the initialing self-antigen is known, the time-point for triggering IDDM can be experimentally chosen and the kinetics of islet infiltration/destruction have been precisely mapped. This allows a segregation of autoreactive lymphocytes from bystander regulatory cells and precise tracking of self (LCMV) reactive T-lymphocytes.